The present invention relates to electro-mechanical systems for inspecting the inside of pipes for defects and obstructions, and more particularly, to a push-cable for use in such a system that mechanically and electrically connects a video camera head to a push reel and video circuit.
There are many situations in which it is desirable to inspect the inside of a pipe which is already in place, either underground, in a building, or underwater. For example, pipes designed to carry high-pressure steam can be internally inspected to determine if there are any cracks in the welds. Sewer pipes or drain lines can similarly be internally inspected to determine whether or not there are any obstructions or degradations in couplings which prevent free flow of waste material. Frequently, pipes which are to be inspected have an internal diameter of six inches or less. It is sometimes necessary to inspect several hundred feet of pipe.
Over the years, video pipe inspection systems have been developed which typically include a camera which is forced down the interior of the pipe so that its internal walls can be inspected on a video display. Conventional video pipe inspection systems include a push-cable which provides an electro-mechanical connection between a rugged head enclosing the video camera and a rotatable push reel which is used to play out the cable and force the head down the pipe. Typically, the push-cable has a co-axial configuration. Both the relatively stiff mechanical portions of the cable and the electrical conductors thereof are arranged in a bundle having a substantially round cross-section. Problems arise because the cable must be sufficiently stiff in order that the head containing the video camera can be pushed hundreds of feet down the inside of a pipe. However, the cable must also be sufficiently flexible so that the video camera head can be forced through a number of tight turns which may include relatively sharp angles, such as ninety degrees. Also, because of the unitary construction of the push-cable typically used in conventional video pipe inspection systems, it is difficult to separate the mechanical and electrical connections in the video camera head in a reliable, efficient manner that will ensure against shorts and de-coupling during the substantial forces encountered during pushing and pulling.